Saturday, February 18, 2012

The parts assembled


This is my rendition of a Sixteenth Century stonebow, modeled in the free version of Google Sketchup.  It resembles an illustration in the Payne-Gallwey book on crossbows.  I had to wing it in a few details because of my skill limits in the program.  I also found that some of the parts from the plans shown by the author did not fit together well; some may have been from different models judging by the proportional errors.  I'm also  not sure of some of the mechanical details.  For instance, I haven't yet come across an explanation of the proper relationship between the bow and the stock which allowed the bullet to pass over the end of the stock without hitting it.  I ended up giving my bow a bit of dihedral, but I doubt that was the actual bowyer's solution.

Below is the stonebow as it appears in Google's 3D Warehouse.  By clicking on the image, the viewer can drag the mouse cursor to rotate the bow in 3D space.


Being able to manipulate a 3D model on my computer screen was something I wanted to do ever since I saw the first examples of it on some of the early personal computers.  I'm happy to stop at that.  Others who use Sketchup and similar programs go the extra step of translating the images into real-world objects.  Aircraft modelers typically print out cross-sections of their creations to use as patterns to be cut from plastic foam.  More recently, designers are producing complex models and prototypes directly from the computer designs using 3D printers.

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